NIMG-50SURVIVAL RATE PREDICTION IN PATIENTS WITH GLIOBLASTOMA MULTIFORME (GBM), USING DYNAMIC CONTRAST ENHANCED MRI AND NESTED MODEL SELECTION TECHNIQUE (NMS)

Abstract

Dynamic Contrast Enhanced MRI is being widely used in research and the clinic for grading and evaluation of response to therapy of solid tumors. Prediction of patient survival can play an important role in treatment planning. In this study, using a pharmacokinetic Nested Model-Selection (NMS) technique, 3 different physiological models (1, 2 and 3) were introduced for estimating the following tumor physiological parameters respectively: plasma volume (vp), vp and forward vascular transfer constant (Ktrans), vp, Ktrans and reverse vascular transfer constant (Kep). This pilot study investigates the predictive power of different permeability parameters estimated by the NMS technique for survival of 20 treatment naive patients with GBM. The MR experiments were performed on a 3 Tesla (Signa-Excite, GE) as following: Variable-Flip-Angle (20, 50, 100, 150, 200 and 250, TR = 5.87ms), 3D-SPGRE (flip angle: 300, TR/TE = 5.8/0.84ms, 256 × 256, 5.7 sec temporal time, 16 slices, Magnevist: 0.1mol/kg, 4ml/sec). NMS was used to estimate all the model parameters (vp, Ktrans and Kep). A Cox proportional-hazards regression (CPHR) model (P-value < 0.05, Confidence Level = %95) was used to analyze the survival time of the patients. According to Wald test and p-values estimated by CPHR analysis for all the parameters of the 3 models, only parameters of model 3 (Ktrans, Kep and Ve with p-value of 0.02, 0.027 and 0.025 and Wald test values of 5.4, 4.8 and 5 respectively) provided the best predictors of survival time among the other parameters. The results show an inverse relationship between Kep and survival, while a direct relationship between Ktrans and Ve with survival (i.e., patients with higher values of Ktrans and Ve showed an improved survival) was observed. In conclusion, using NMS technique, this pilot study suggests a possible association between survival and Ktrans, Kep, Ve in GBM patients that may be of considerable clinical importance.